What is the refractive index of water ?

Explanation

` A = 60^(@) , D_(m) = 40^(@)`
n ` = (sin ((A + D_(m))/(2)) )/( sin((A)/(2))) = (sin ""((60 + 40)/(2)))/( sin((60)/(2))) = 1.53 " " n_(gw) = (n_(g))/(n_(w)) = (1.53)/(1.53) = 1.15`
`n_(gw) = (sin ((A + D_(m))/(2)) )/( sin((A)/(2))) " " i.e., 1.15 = (sin"" ((60 + D_(m))/(2)))/( sin 30 )`
`therefore sin ((60 + D_(m))/(2)) = 1.15 xx sin 30 = 0.573 `
` (60 + D_(m))/(2) = 35^(@) 6.`
`D_(m) = 70^(@) 12. - 60^(@) = 10^(@) 12.`